1. Field of the Invention
This invention relates to stairway ramps and the like used to provide a transfer structure for wheeled dollies or wheelchairs thereby enabling access to two areas of unequal height connected by a stairway.
2. Description of the Prior Art
Prior art devices have relied on a number of different designs. In U.S. Pat. No. 4,528,711 to Packer, a vehicle wheelchair ramp is disclosed having a pair of ramps telescopically engaging one another that are U-shaped in cross section. A pair of transversely positioned elongated spacer brackets are attached to the ramps to provide uniform transverse spacing of the ramps. The ramps can be detached from one another, collapsed and secured together for ease of transport.
An alternate approach in providing a stairway ramp is disclosed in U.S. Pat. No. 4,712,264 to Voith. The Voith ramp is constructed from a plurality of right triangular modules which nest in the recesses of a stairway. The modules are securely and releasably interconnected by tethered locking pins received by registering locking apertures of male and female connector elements. A continuous stairway ramp formed by two parallel groups of modules is laterally adjustable through connector slides on the riser walls of the modules.
Other stairway ramp devices are disclosed in the following patents: U.S. Pat. No. 981,613 to Carter; U.S. Pat. No. 1,506,116 to Wiebe; U.S. Pat. No. 2,312,273 to Stochmal; and U.S. Pat. No. 3,009,183 to Lay. The prior art devices are limited in several respects with regard to ease of portability, dismantling and reassembly, adjustability to accommodate varying stairway inclination angles as well as length of stairways, and cost of manufacture. A new stair track apparatus having greater flexibility to accommodate a wide variety of stairways having diverse dimensions is needed.